1. Field of the Invention
The invention relates to the construction area, particularly to the area where existing low-storied buildings are to be transformed into high-storied buildings, i.e., adding additional stories to existing low-storied buildings.
2. Description of Related Art
The addition of additional stories to existing low-storied buildings is a new theme in the development of urban construction all over the world. With the increase of urban populations, cities are bound to expand, but owing to the limitations of cultivated areas, the actual area of individual cities cannot be enlarged at will. It is therefor necessary to confine development to within the scope of the city proper. This requires raising the height of buildings in the city, especially where the original buildings are generally very low in height, where the contradiction between reality and requirement is most prominent. Up to now the solutions to this contradiction involve:
1. Demolishing the original low-storied buildings and reconstructing new high-storied buildings at the site. In so doing, not only do there arise the problems of moving residents to other places, as well as the disposal of waste from the construction site, but also that some of the buildings must be forced down notwithstanding the fact that they are far from service maturity. This causes extravagance and waste, as well as some social problems that are difficult to solve.
2. Raising the height of the original buildings.
At present, raising the height of buildings comprises mainly two processes:
a) The original building is retained, and one to two stories are added to it; and
b) More stories are added by means of a pure frame structure.
In process a), the weight of the additional stories are to be supported by the original building structure. However, as the bearing capacity of the original building structure is quite limited, only one or two stories can be added at the most. Obviously, this cannot satisfy the requirement of raising the height of the buildings. In process b), the weight of the added stories cannot be transmitted to the foundation via the frame structure, because the frame structure has not taken into consideration in its design the precise route of force transmission of the added structure of the stories, i.e., there should be no confusion regarding the route of force transmission. In addition, no measure is taken to avoid sliding of the foundation, possibly occurring during an earthquake. Therefore, this kind of story-added structure not only presents intrinsic faults regarding the principle structural design mechanics, i.e., the confusion of the routes of force transmission of the structure, but also its earthquake resistance is very low.
The object of this invention is to provide a method for adding additional stories to an existing low-storied building for raising the height of the existing low-storied building, in which the weight of the newly-added multi-storied building portion is transmitted to the ground base via a weight supporting frame structure specifically connected to the original building, rather than supported by the original building, so that the routes of force transmission of the added integral structure, in any circumstance, (including earthquake, shock load) will not be confused. In the meantime, there are incorporated in this invention three items which are subjects of pending patent applications, namely, "Devices of Shock Resistance and Shock Absorbing for Buildings" (Chinese Patent Application No. 87100151); "Shock Isolator for Buildings" (Chinese Patent Application No. 88108470.0); and "Connectors Between New and Old Structures in Raising the Height of Old Buildings" (Chinese Patent Application No. 89106137.1) for realizing the above-mentioned specific connection. In addition, a stress superimposed area of the ground base is provided with an anti-slide plate, so that the aseismic capacity of the integral structure of the stories-added low-storied building is substantially increased.
The method according to the invention for accomplishing the above-mentioned objects is as follows.
Closely around the original building is laid a foundation upon which several story-adding supporting frame columns are erected. Structure expansion & contraction joints are provided between the original building and the columns and these joints can be filled with compressible material.
Story-adding frame supporting girders are fixedly connected with said frame columns above the roof of the original building so that the weight of the story-adding structure is to be supported by the girders and to be transmitted to the ground base via the frame columns. The bottom surface of the girder and the top surface of the original building are separated by a space, the dimension of which should be bigger than the amount of sinking of the story-adding structure.
The frame columns are connected at the floor place of every story of the original building to the columns of the original building by means of the connectors between new and old structures, as disclosed in Chinese Patent Application No. 89106137.1, assuming a connection by oriented pivotal bearing, for example, the end of the frame column being a fixed end while the end at the column of the old building a vertically movable hinge end, where sideways moving is not permitted.
Close at the outer side of the foundation of the story-adding supporting frame column and below the bottom of the foundation there is provided an anti-sliding plate for ground base soil, for example, using a reinforced concrete plate.
Between the foundation of the original building and the newly-added foundation of the supporting frame columns is provided a partition made of hard and thin material.
In order to enhance the stability of the newly added story-adding supporting frame columns, they are connected to each other lengthwise along the original building at the level of every corresponding floor place thereof by means of the plate beams.
It is understood that the structure of the original building is basically stable after many years of use, so that it may be deemed a non-deforming rigid body. The story-adding structure, at an early stage of use, may present sinking of foundation and self-deformation of the structure members after subjecting to load, resulting in a vertical relative displacement, between the new and old buildings. Consequently, if no appropriate measures are taken, or no specific connections are provided between the old and new buildings, but rather, a conventional rigid connection is still employed, the weight of the new building would surely press down on the old building resulting in a confusion of route of force transmission and the increase of stress within the old and new structures. However, as there is provided, according to the present invention, a certain space between the bottom surface of the story-adding frame supporting girders an the top surface of the original building, particularly as the connectors between new and old structures employed between the new and old buildings are oriented pivoted bearings, it not only can avoid the above-mentioned defects, but also can shorten the free length of the story-adding frame columns, enhance the stability of the story-added structure and the integrity with the old building so as to improve the aseismic capacity of the overall building.
Furthermore, as there is provided an anti-sliding plate for ground base soil as mentioned above, it can prevent the ground soil under the new building foundation from being squeezed out in a direction away from the original building, thus preventing the foundation from sliding. This also enhances the aseismic capacity of the building.
Besides, as the foundations of the old and new buildings are arranged close to each other, the span length of the girders are shortened, and as they are separated from each other by a partition, it can prevent the foundation of a new building from affecting the foundation of the original building before it reaches its stability.
The method, objects and advantages of the invention will now be described in detail by reference to the accompanying drawings, in which the same reference number will be applied to the same or corresponding part.